Electric crane.



No. 771,987. PATENTED OCT. 11, 1904. H. A. LEWIS.

ELECTRIC CRANE.

APPLIGATION FILED DEC. 30, 1903.

"NO MODEL.

ATTORNEY.

UNITED STATES Patented October 11, 1904f PATENT OEEicE.

HARRY A. LEWIS, OF NORRI STOWVN, PENNSYLVANIA, ASSIGNOR OF ONE- HALF TO ALAN D. VOOD, OF CONSHOHOOKEN, PENNSYLVANIA.

ELECTRIC CRANE.

SPECIFICATION forming part of Letters Patent No. 771,987, dated October 11, 1904.

Application filed December 30,1903. Serial No. 187,163. (No model.)

the invention, stated in general terms, comprises a normally open branch circuit provided with means responding to the limit of motion of the crane and adapted to establish said branch circuit, whereby the motor is ar rested in one direction, but is ready to start in the other direction in response to the proper positioning of its reversing switch or controller; and the invention further comprises the improvements to be presently described and finally claimed.

' The nature, characteristic features, and scope of my invention will be more fully understood from the following description, taken in connection with the accompanying drawings, forming part hereof, in which Figure 1 is a view illustrating diagrammatically a crane embodying features of the invention. Fig. 2 is adiagrainmatic view illustrating the position of the parts during hoist. Fig. 3 is a similar view illustrating the parts in the position in which they are automatically arrested. Fig. 4 is a diagrammatic view of a controller or reversing switch, and Fig. 5 is a view illustrating a detail of construction.

In the drawings, 1 is the motor, which drives the hoist or drum 2 through the intervention of suitable gearing, and there is a circuit maker and breaker which responds to movements of the motor 1. breaker 3 is geared to the drum 2. The type of circuit breaker and maker illustrated comprises a rotary disk, Fig. 5, having upon its periphery an insulated bridge 4, arranged in one position of the drum to bridge a pair of contacts 5.

6 indicates a brake normally solicited, as

tion for bridging it.

As shown, a circuit-- by a spring, into position for arresting the motor andadapted to be drawn free. of the motor by a solenoid or electroinagnet '7.

8 is a controller or reversing switch which serves to run the motor in one direction or the other, as may be required. It, as well as the automatic circuit-breakers 9 and 10, are usually arranged in the car or cabin and within reach of the operator.

The circuits will now be traced when the hoist is lifting, and reference is made to Fig. 2. One side of the line enters by conductor (1 passes field and automatic circuit-breaker 10 and reaches point a of the controller. From thence it passes by controller bridge (f through the resistance R to point a" of the controller, then by bridge a of the controller to motor circuit conductor a thence through the solenoid or electromagnet 7 when present, and thence through the motor-arma ture and by motorarmature conductor a through the circuit-breaker 9 to controllerpoint a by controllerbridge (6S and to the conductor a, which constitutes the other side of the line. The branch circuit, comprising the conductors Z) and b and contacts 5 and 6, is open, because the bridge-piece L is not in posi- Under these conditions current passes by a through the controller, holds the brake 6, if present, out of operation, operates the motor, and returns by conductor a through the controller and back to line by conduetor a. If it be assumed that through some oversight or neglect the part driven bythe motor is permitted to travel so as to approach the limit of its safe movement the circuit maker and breaker 3 will have closed the branch circuit Z) and 6'. Under these conditions the circuits have changed, and they will now be described. The path of the current instead of being from a to the motor-armature will be diverted through 7), 4:, and 7/ to the line (0. 'Thus the armature of the motor is out out of circuit, so that the motor will stop and the magnet of the brake device, if present, is deenergized, so that the brake comes into action. Furthermore, the effect of this is to probably throw the automatic circuitbreakers 9 and 10. From the foregoing it is obvious that the motor is automatically stopped, so that the crane or hoist cannot overtravel, and accidents are thereby guarded against and avoided.

To start the motor again, the operator positions his controller or reversing switch to run the motor in the direction opposite to that in which it was running when automatically arrested in the manner described. Referring to Fig. 3,we find that the result of this is to change the circuits, and they will now be described. Current enters by a, traverses the.

controller-bridge c and the resistance R and the controller-bridge 0, and thence passes by conductor a through the motor-armature and by the conductor a through the brake-magnet, when present, so as to release the brake, thence by the branch circuit 6, 4, and Z2 and back to line a". Of course the circuit-breakers 9 and 10 are assumed to be closed. The result of this is that the motor starts and runs in a direction opposed to that in which it was traveling when automaticallyarrested,and the start is made by the operator without leaving his position and without having to do anything more than adjust his reversing-switch and close the circuit-breakers, if they have been blown. Of course a start in this direction breaks the continuity of the branch circuit 5 I); but that is immaterial, because the current instead of reaching a by way of b and b, as before, does so by way of a and the controller bridge-piece c.

It will be obvious to those skilled in the art to which my invention appertains that modifications may be made in detail without departing from the spirit thereof. Hence I do not limit myself to the precise construction and arrangement of parts hereinabove set forth, and illustrated in the accompanying drawings; but,

Having thus described the nature and objects of my invention,what I claim as new, and desire to secure by Letters Patent, is

1. The combination in an electric crane of a moving part of which the range of lift travel should be limited, an electric motor for moving said part, a line-circuit in which the motor field and armature are normally included, a switch normally out of the circuit and having connections for short-circuiting the motorarmature and adapted to short-circuit the armature in response to the limit lift movement of said part, and a controller adapted to reverse the motor connections and provided with circuit connections for short-circuiting the switch to permit of running the motor to lower said part, substantially as described.

2. The combination in an electric crane of a moving part of which the range of lift travel should be limited, an electric motor for moving said part, a line-circuit in which the motor field and armature are normally included, a switch having connections for short-circuiting the motor-armature and adapted to shortcircuit the armature in response to the limit lift movement of said part, a controller adapted to reverse the motor connections and provided with circuit connections for short-circuiting the switch to permit of running the motor to lower said part, and automatic circuit-breakers interposed in the armature and field-circuits for protecting the motor armature and field when the armature is short-circuited, substantially as described.

3. The combination in an electric crane of a line-circuit, a moving part of which the travel is to be limited, a safety-switch responsive to the limit movement of said part, a motor, a controller, a conductor from the line to the controller, one field and two armature conductors from the controller and whereof the field-conductor goes to the motor-field and whereof the two armature-conductors go to the n1otor-armature, a conductor from the motor-field to line, and a conductor from said field-conductor through the safety-switch to one of said armature-conductors, substantially as described.

4. The combination in an electric crane of a line-circuit, a moving part of which the travel is to be limited, a safety-switch responsive to the limit movement of said part, a motor, a controller, a conductor from the line to the controller, one field and two armature conductors from the controller and whereof the fieldconductor goes to the motor-field and whereof the two armature-conductors go to the motor-armature, a conductor from the motorfield to the line, a conductor from said fieldconductor through the safety-switch to one of said armature-conductors, and means interposed in the armature-circuit between the armature and controller for protecting the armature when short-circuited by the safetyswitch, substantially as described.

5. The combination in an electric crane of a line-circuit, a moving part of which the travel is to be limited, a safety-switch responsive to the limit movement of said part, a motor, a controller, a conductor from the line to the controller, one field and two armature conductors from the controller and whereof the field-conductor goes to the motor-field and whereof the two armature-conductors go to the motor-armature, a conductor from the motor-field to the line, a conductor from said field-conductor through the safety-switch to one of said armature-conductors, and means interposed in one of said armature-conductors to protect the armature when short-circuited, and devices interposed in the conductor which lead from the motor-field to the line to protect the field of the motor, substantially as described.

In testimony whereof I have hereunto signed my name.

HARRY A. LEWIS. In presence of O. F. LENHARD, JOHN J. GRUBER. 

